1. Field
The present disclosure relates generally to aircraft and in particular, to control surfaces for aircraft. Still more particularly, the present disclosure relates to a computer implemented method, apparatus, and computer program code for manipulating control surfaces to reduce loads on an aircraft.
2. Background
Control surfaces are airfoils that deflect air in one direction and cause an aircraft to move in the opposite direction. Control surfaces are also referred to as flight control surfaces or flight controls. As used herein, an aircraft includes, without limitation, an airplane, a helicopter, a carrier, a commercial airliner, a sea plane, or any other type of aircraft.
Control surfaces are manipulated by pilots or by control laws to move an aircraft about its axes of motion and/or change an orientation of the aircraft. Control surfaces are frequently manipulated by using control devices such as a control yoke, a control stick, and/or pedals. Control surfaces may also be manipulated by control laws and/or logic in response to external gust or pilot commands input using a control device.
Control surfaces include, without limitation, ailerons, flaperons, rudders, spoilers, elevators, trim devices, and flaps. The ailerons, spoilers and flaperons are used to bank or roll an aircraft about the aircraft's longitudinal axis. The rudder yaws an aircraft about a vertical axis. The elevator moves an aircraft about the aircraft's lateral axis to change the aircraft's pitch attitude. Utilization of symmetric flaperons results in vertical motion of an aircraft.
For example, the pitch of an aircraft may be changed using elevators located on the horizontal tail of an aircraft. The pitch of an aircraft may cause the nose of the aircraft to go up or down. An elevator may be moved upwards, with trailing edge up, to cause the pitch of the aircraft to be upward.
The elevators may be moved downwards, with trailing edge down, to cause the pitch of the aircraft to be downward. An elevator decreases or increases the downward force caused by the tail. An increased downward force is produced by the elevator moving up, which forces the tail down and the nose up. When the elevator moves down, with trailing edge down, an upward force occurs on the tail when the elevator is moved down to force the tail up and move the nose down.
The changing of the position of the elevator may change the load that is placed on the tail of an aircraft. This load may be on the horizontal tail as well as structures within the tail of the aircraft. Currently, the speed of an aircraft has been used to limit the amount of load that may be generated by an elevator. The movement of the elevator may be limited based on the speed of the aircraft.
However, these traditional limits are not able to be set too strict to handle extreme maneuvers since strict limits would affect the maneuverability of the aircraft in other flying patterns. As a result, additional structures are needed to handle the load caused by these extreme maneuvers.
The different advantageous embodiments recognize that in designing an aircraft, structures in an aircraft are required to take into account peak structural loads during extreme maneuvers using control surfaces such as elevators. The different advantageous embodiments recognize that these structural requirements add to the weight of an aircraft.
Therefore, the different advantageous embodiments recognize that it would be desirable to have a method and apparatus to alleviate loads on control surfaces, such as a tail of an aircraft.